Serial mouse
Pin Description 1 DCD Data carried detect 2 RD Receive data 3 TD Transmit data 4 DTR Data terminal ready 5 SG Signal ground 6 DSR Data set ready 7 RTS Request to send 8 CTS Clear to send 9 Ring
eg: Serial control for NEC projectors LT240,260,245,265.....and others.
This is the "standard" Mac serial din-8 out pinout.